Currently available adhesive systems are typically based on polymeric materials that can be divided into one of two classes, thermoset or thermoplastics. Although the thermoset class inherently has better cohesive strength, is thermally stable, and in general, can be formulated to adhere to a wide variety of substrates, the thermoplastic adhesives or hot-melt adhesives are preferred. These adhesives develop their bond strength almost instantaneously, requiring virtually no time for cure and can be applied and reactivated relatively easily under severe environmental conditions. The hot-melt adhesives have found wide applications in the commercial market to provide bonding of a wide variety of materials.
The first commercially available hot-melt adhesives were packaged as glue sticks that were utilized in conjunction with a glue gun to apply the glue at temperatures of around 380.degree. F. The viscosities of these early glue sticks upon application was around 9000 cps; they had a rather sharp viscosity curve and were not very useful at lower temperatures. Applications of a glue to material that was heat sensitive below 380.degree. F. essentially precluded the use of these hotmelt adhesives. As a result, low temperature hot-melt adhesives were developed. Examples of these are described in U.S. Pat. No. 5,041,482 and U.S. Pat. No. 4,986,680. These low temperature hot-melt compositions required a special glue gun that operated at a temperature of around 250.degree. F. The viscosity exhibited by these low temperature hot-melt compositions was around 4900 at 250.degree. F. However, their viscosity at 380.degree. C. was less than 600 cps. As a result, if these glue sticks were utilized in a glue gun that had application temperatures of 380.degree. F., i.e., a high temperature glue gun, they would exhibit a very "runny" composition and would provide little utility. However, if the opposite occurred wherein a high temperature hot-melt adhesive composition were utilized in a stick form with the low temperature glue gun, the viscosity of these materials would be in excess of 100,000, and, as such, they would not freely flow and would result in jamming of the glue guns. As a result of this, glue guns were developed having two application temperatures. One solution to multiple glue sticks is to design one of the guns to utilize a different shape for the glue stick.
One disadvantage to having both high temperature and low temperature glue sticks is that a commercial establishment must now not only carry glue guns that are capable of multiple application temperatures, but also, the establishments must stock two types of glue sticks. This creates problems from both an inventory standpoint for the retailer and the use by the purchaser.